Open-closed principle and Java “final” modifier

Question

The open-closed principle states that \"Software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification\".

However, J

Answer 1

I respect Joshua Bloch a great deal, and I consider Effective Java to pretty much be the Java bible. But I think that automatically defaulting to private access is often a mistake. I tend to make things protected by default so that they can at least be accessed by extending the class. This mostly grew out of a need to unit test components, but I also find it handy for overriding the default behavior of classes. I find it very annoying when I'm working in my own company's codebase and end up having to copy & modify the source because the author chose to "hide" everything. If it's at all in my power, I lobby to have the access changed to protected to avoid the duplication, which is far worse IMHO.

Also keep in mind that Bloch's background is in designing very public bedrock API libraries; the bar for getting such code "correct" must be set very high, so chances are it's not really the same situation as most code you'll be writing. Important libraries such as the JRE itself tend to be more restrictive in order to ensure that the language is not abused. See all the deprecated APIs in the JRE? It's almost impossible to change or remove them. Your codebase is probably not set in stone, so you do have the opportunity to fix things if it turns out you made a mistake initially.